Piston-mounted end lock for hydraulic actuators



wt. 25, 1956 E. H. BAKKE 2,764,132

PISTON-MOUNTED END LOCK FOR HYDRAULIC ACTUATORS Filed May 6, 1954INVENTOR. 506,42 4. EAL/K5 BY I ATTORNEY-5 United States Patent GPISTON-MOUNTED END LOCK FOR HYDRAULIC ACTUATORS Edgar H. Bakke, Seattle,Wash., assignor to Boeing Airplane Company, Seattle, Wash., acorporation of Delaware Application May 6, 1954, Serial No. 428,063Claims. (Cl. 121-40) Hydraulic jack means, or struts, are used, inaircraft construction particularly, as a means of effecting movement ofa controlled part from one position to another. It is usually desirableto lock the strut in at least one position, and frequently in each limitposition. As an example, hydraulic jack means are employed to move alanding unit from a retracted to a projected, or landing, position andvice versa, and it is essential that the landing unit be locked in eachsuch limit position against the possibility of accidental movementtherefrom. Such locking mechanism should be positive and mechanical, toguard against the possibility of failure or leakage in the hydraulicsystem. In addition, it is desirable that such locking mechanism bereleasable in advance of, and often desirably by the same pressure fluidas is employed to effect, actuation of the jack means, or strut, fromits locked position. v

Mechanisms to the general ends above are old and Well known. A highlydesirable form of such mechanism is disclosed in the co-pendingapplication of Richard A, Chace and George C. Newell, Ir, Serial No.355,522, filled May 18, 1953. This particular mechanism is desirable inthat it employs toggle link mechanism mounted upon one of the relativelymovable members of the jack, in conjunction with looking dogs carried bythe same member, and projectable and retractable with respect to thatmember, which locking dogs are beveled at their outer ends forinterengagement with a similarly beveled shoulder on the other member ofthe jack or actuator, being the member which does not carry the togglelink mechanism and the locking dogs. In the Chace and Newellarrangement, the toggle link mechanism and the locking dogs, andpressure actuated means for initiating release of the lock, are allcarried by the cylinder head, and the complemental beveled shoulder iscarried by the piston. While two such mechanisms might be employed, oneat each end of the cylinder, it is believed to be preferable, and moreeconomical of space and weight, to mount two such locking mechanisms inthe piston and to engage them alternatively with beveled shouldersprovided in the cylinder Wall adjacent the respective ends of thecylinder. The present invention is concerned, therefore, withincorporation of the general principles disclosed in the Chace andNewell application, in a construction wherein the locking devices andthe actuators therefor are all mounted in and movable axially with thepiston, and the cylinder is provided simply with two com plementalbeveled shoulders. The Chace and Newell application disclosesspecifically a form wherein the piston is skirted and the skirt thereofis formed internally with a beveled circumferential groove; thecooperating toggleactuated locking devices are supported from thecylinder head, in position to project axially within the pistons skirtwhen the piston reaches a limit position at an end of its travel.projectible r-adially outwardly into engagement withthe groove of thepistonsskirt. The specific disclosure of Thereupon the locking devicesare 2 the Chace and Newell application is of a lock only of the pistonstravel.

In distinction to the above, the specific disclosure of this applicationincludes a lock at both ends of the pistons travel. The presentdisclosure accomplishes this by reversing the arrangement in the Chaceand Newell disclosure, in that the toggle-actuated locking device-in thepreferred arrangement, for convenience, two such locking devices, eachwith its toggle actuator-is mounted within the piston for bodilymovement axially therewith, wherefore the complemental beveled groove isformed in the respective ends of the cylinder wherein the piston isaxially movable.

This application is generic to the idea of effecting a lock by such atoggle-actuated locking device at each end of the travel of a piston orlike guided element, Within the cylinder or corresponding guide for thesame. Contrariwise, the Chace and Newell application is generic to theidea of the toggle-actuated locking device, including the beveled groovein one such relatively axially movable component and the complementallybeveled locking dog means in the other such component, radiallyshiftable in the locking sense under the influence of the toggle links,and in the releasing sense under the influence of the axial forceapplied to the two axially movable components and communicated to thelocking dog means through its beveled surface or the beveled surface ofits engaged groove, whether that generic idea be incorporated in thedouble-ended form disclosed in this application, or in the single-endedform disclosed in the Chace and Newell application, or whether the samebe incorporated in a cylindenmounted locking device as in thisdisclosure, or in connection with a locking device that is mounted in orsupported from the cylinder head, as in the Chace and Newell disclosure.

One of the advantages inherent in this and in the Chace and Newellstructure is that by the use of the beveled shoulders, and of rotatabletoggle links which hold beveled locking dog means in secure engagementwith such shoulders, it is possible by rotation of the toggle links fromtheir locked, or aligned, positions with respect to the locking dogmeans, to effect sudden collapse of the lock after extremely slightrelative movement be tween the interengaged beveled surfaces, and Whilethere is still substantially full face engagement between such surfaces.As a result there is no gradually decreasing area of contact betweenlocking dog means and the shoulders they engage, until ultimatelythearea of contact becomes zero, all the while a strong force is urgingparts to movement in opposition to the look, It follows that the suddencollapse, possible by virtue of the principles disclosed in the Chaceand Newell application, avoids the grinding away of metal, which is theinevitable result of such sliding movement to zero contact under heavypressure, and eliminates the necessity for frequent replacement ofparts,o1' alternatively, the danger of failure due to wear of the parts.The same advantages are capable of achievement by the present invention,in a constructional arrangement wherein the locking dog at one endmeans, the toggle links, and the plungers for effecting releasingmovement of the same, are all mounted in the piston element of theactuator, and wherein preferably the cooperating beveled surfiaces areduplicated at the opposite ends of the piston, to elfec-t locking andreleasing at the two limit positions.

Whereas the Chace and Newell specific disclosure is of a single end lockonly, the disclosure herein is of a double-end lock. inasmuch as eachsuch lock is releasable byapplication locking, effects reciprocativemovement of the piston within the cylinder, it is oneof the objects ofthis invention to provide a construction including yield'able meof thesame pressure which, upon un-' axially disposed bore of the piston.

'posite face of the piston.

chanical biasing means, operable in addition to hydraulic biasing means,and capable of retaining parts in either locked position, againstaccidental hydraulic release, even though there may be. a momentary surgof pressure in one side or the other of the cylinder.

In accordance with the specific disclosure of the present invention, andwithout limitation of its scope, otherwise than as is indicated in theclaims, there is, according to the present invention, a cylinder and apiston which is slidably fitted therein for reciprocation between twolimit positions, the cylinder having ports for admission of pressurefluid to each end thereof, and for discharge of such pressure fluid, andthe two locking devices, both carried by the piston but one adjacenteach end face thereof, each includes one or more locking dog means (ashereinafter defined more specifically), one element or more of which isguided in the piston for radially outward and inward movement, a togglelink rotatable to effect such movement of each locking dog means, andmovable by such rotation into alignment with its locking dog means. Suchmovement of the toggle link is effected by a pressure-fluid-actuatedplunger axially reciprocable in an Each such locking dog means, or theradially outermost element thereof, is beveled complementally to and forengagement with a beveled shoulder at the respective ends of thecylinder. Each such actuating plunger is received Within its bore in thepiston, defining thus a pressure chamber behind the plunger which isported for communication with the op- Thus, as pressure fluid isadmitted into one end of the main cylinder and applied to one face ofthe piston to urg the latter towards the opposite end, the same pressureis applied to the outer end of the plunger that protrudes from the sameface of the piston, to urge that plunger towards unlocked position. Thisplungers pressure chamber, communicating with the opposite face of thepiston, is vented to low pressure, hence the plunger shifts inwardly, inopposition to spring means, and the lock is thereby suddenly released.Movement of the piston towards its opposite limit position ensues.

Since the other plungers pressure chamber, at the opposite (now lowerpressure) face of the piston, is in communication with the now higherpressure face, this higher pressure tends to urge this second plungeroutwardly in its bore, and so to move the locking dog means for theopposite end into locked position. This it can not do until it reachesthe opposite limit position, for projection of the locking dog means isrestrained by their engagement with the cylinder wall, but once thepiston reaches that opposite limit position, the plunger is shifted inits bore by the still-applied pressure and the locking device at thisend comes into locking engagement with the beveled shoulder at this endof the cylinder.

The locking dog means may take the simple form of the Chace and Newellarrangement, or on the other hand, it is preferred that it take the formof a substantially circular segmental ring, which is received andretracted within a groove of the piston during movement of the piston,but which can be expanded and moved out of that groove into engagementwith a circumferential groove of the cylinder wall in the lockingposition of the parts. This specific form lessens the loading on anygiven area, distributing it instead over virtually the entire circle ofthe groove.

The drawings and this specification are to be under stood asillustrative rather than as restrictive, other than as is required bythe language of the accompanying claims.

Figure l is a longitudinal axial sectional view through the actuator,showing parts locked in the limit position of closest approach betweenits end fittings.

Figure 2 is a transverse sectional view on the line 22 of Figure 1, andFigure 3 is a similar transverse 4 sectional view, but showing parts inthe retracted, or unlocked, position.

The actuator comprises a main cylinder 1 closed at its ends, and thepiston 2 slidably fitted therein for reciprocative movement from one endof the cylinder to the other, its two faces being sealed from oneanother by suitable sealing means indicated at 20. The piston rod 21projects through one end of the cylinder, where it is formed with anattachment end fitting 22, and the opposite end of the cylinder isformed with an attachment end fitting 12. Provision is made foradmitting pressure fluid to and relieving the same from each such end.The precise manner of doing this is immaterial, and there are shownports 11 at one end and 13 at the opposite end. Such details of theactuator are common and, in themselves, are not part of this invention.

Adjacent one end of the cylinder, its interior wall is formed with abeveled shoulder, preferably in the form of a circumferential groove orshoulder, as indicated at 14, and a similar shoulder 15 is formed at itsopposite end. These shoulders 14 and 15 may be taken as defining, in asense, the opposite limits of movement of the piston.

The piston is somewhat elongated axially and is axially V bored fromeach face as indicated at 23 and 24. A plunger 3 fits and slides axiallywithin each bore, being exposed at its outer face to the sam pressure asis applied to the corresponding face of the piston, and a smallerextension at its inner end fits slidably within a smaller interiorchamber defined by the cylindrical wall 27 extending axially andupstanding from the bottom of each bore. Port 28 affords communicationbetween the lefthand end of the piston and this small chamber behind theright-hand plunger 3, and in like fashion, port 29 affords communicationbetween the right-hand end of the piston and the small interior chamberbehind the lefthand plunger 3. The purpose of these ports will appearshortly. Spring means 31 urge the respective plungers 3 axiallyoutwardly in their bores. Stop means to be described later limit suchprojective movement.

Radial guide apertures 25, of which there are preferably several,equiangularly spaced, intersect each bore 23 and 24. Preferably, also,the piston 2 is formed with a circumferential groove 26 (see Figure 2)into which the radially outer ends of the radial guide apertures 25admit. Radially slidable elements 4 of locking dog means, to bedescribed later, are guided for radial sliding movement in theseapertures 25.

The plungers 3 are, in effect, independently operable actuators for theindividual locking means, one at each end of the cylinder. The plungers3 are movable under the influence of the compression spring means 31, oradditionally, by pressure admitted behind the small inner end of theplunger 3 within the chamber wall 27 by way of the ports 28 or 29 fromthe opposite face of the piston. When the plungers 3 are moved inwardlyof their bores under the influence of pressure applied to the outer faceof the plunger and likewise to the corresponding end of the piston, theports 28 and 29 constitut vent ports to relieve and vent the fluidbehind the smaller inner ends of the respective plungers.

Locking dog means, which term is intended to cover generically variousforms of the dog means, such as that shown in the Chace and Newellapplication, or the means specifically disclosed herein, are providedfor locking engagement with the shoulders 14 and 15, respectively. Suchlocking dog means include the referred to radially movable elementsguided in the apertures 25, designated herein by the numeral 4, andwhich will be termed herein expanders. It would be possible to form theradially outer ends of these expanders 4 for direct engagement with thebeveled shoulders 14 and 15, after the mannot suggested by Chace andNewell, but preferably the actual locking dog devices are made in theform of a sub t ntially circular, but segmental ring, the segmentswhereof are indicated at 41. Two such circular segmental rings arereceived one within each of the circum ferential grooves 26 of thepiston, and the outer circumference of which rings can be withdrawnwithin the outer periphery of the piston, or can be projected therefrombehind the locking shoulders 14 and 15. The peripheral edge of such aring, composed of the segments 41, is beveled at 40 complementally tothe bevel of the shoulders 14 and 15, as is best seen in Figure 1.border to effect expansion or permit contraction of the ring segments41, their ends are beveled at the inner periphery, and the expanders 4are similarly double-beveled, as seen best in Figures 2 and 3, and asindicated at 44, whereby outward movement of the expanders 4 will reactthrough the double bevels 44 and the complemental bevels on the ringsegments to expand the ring and urge its segments outwardly, andretractive or inward movement of the expanders 4 will permit the ringsegments 41 to retract within their groove 26.

Outward movement of the expanders 4 is accomplished by toggle means,such as the links 5, rockably connected between the plunger 3 and theseveral individual expanders 4. In Figure 1, the right hand plunger 3having been moved to the right with respect to the piston, its togglelinks 5 have been moved into alignment with the direction of movement ofthe expanders 4, and the ring segments 41 at this end of the piston havebeen expanded and are in locked engagement with the shoulder 15. Thetoggle links are held in this locked position by engagement with stopshoulders 30 on the plunger, and similar shoulders on the expander. Thestop shoulders also constitute stops limiting outward movement of theplunger 3 in its bore 23 or 24. At the left hand end of the piston, theplunger 3 is withdrawn into its pressure chamber, defined by the wall27, which has permitted the toggle links 5 at this end to collapse, andthe expanders 4 to move inwardly. This, in turn, permits inward orretractive movement of the ring composed of the segments 41, and partsat this end are in the unlocked position. However, spring means 31 havebeen compressed at this left end, and yieldingly bias the toggle linksto their radially outward aligned position, and the locking dog means tothe locking position. It is restrained, of course, from movement intosuch position by the fact that the outer edge of the ring segments 41bear, without great force, on the wall of the cylinder. At the righthand end, the spring means 31 have been expanded, and have effected themovement of parts at this end into the locked position, aided (if theports 28 and 29 are so located as not to be obstructed by the skirt ofplungers 3) by fluid pressure from behind the advancing plunger 2.

In order to insure the movement of parts to the locked position, it willbe observed that pressure from the left hand end or face of the pistonis applied by way of the ports 28 to the interior of the pressurechamber defined at 27 at the right hand end of the piston. This pressureis applied when parts of the actuator are in the fully extendedposition, with the piston 2 at the left hand end of the cylinder 1. Thefirst effect of the application of pressure through the ports 11 is tourge the piston 2 toward the right hand end of the cylinder, but sinceit is locked by the left hand set of locking dogs, movement can notbegin until the locking dogs at this side of the piston are released.The pressure applies also to the exposed end of the plunger 3 at theleft of the piston, and since its chamber within the bore 27 is ventedby way of the ports 29 to the right hand face of the piston 2, thepressure actin on the left hand plunger 3 urges it to the right, withrespect to the piston 2, and the look at this end collapses. Thepressure continuing to act on the main piston 2, moves it to the right.When it reaches the right hand limit of its movement within the cylinder1, pressure entering by way of the ports 28, which has in the meantimebeen acting on the inner end of the right hand plunger 3, now urges thisplunger outwardly and expands the right hand ring segments 41 intoengagement with the shoulder 15. The plunger 3 at the right moves underthe influence of this pressure and also under the influence of itssprings 31, until the toggle links 5 are stopped in their aligned, andlocked, position. Parts are now locked in the right hand limit positionof the main piston 2. When reverse movement of the piston 2 is required,pressure is admitted at 13, the right hand plunger 3 is pushed inwardlyof its pressure chamber, and the lock at this end is unlocked, whereuponmovement of the piston 21 to the left begins, and the lock isreaccomplished. at the opposite end in engagement with the shoulder 14,in the manner already described.

It will be observed that the larger area of the bores 23 and 24 arevented so that the pressure acts on the respective plungers 3 only tothe extent of the area entered and slidably fitted within the smallerpressure chambers 27. Were it not so, the pressure over the entire areaof the plunger would be rather appreciable, and during sliding of thepiston might cause scoring of the cylinder wall by reason of the forceapplied to the outwardly urged ring segments 41.

It will be observed that the packing seal at 20 is not required to passover any lines of junction or past the respective locking shoulders 14and 15. This is true be cause the locking means are at the respectiveends of the piston, outwardly beyond the seal at 20.

When parts are in the locked position, springs 31 tend to hold the oneplunger 3 projected from its bore, and parts at the one end in lockedposition. Were entire dependence to be placed on hydraulic pressure tokeep parts in locked position, it is possible that a sudden relief ofpressure, or a surge of pressure, in the hydraulic lines to theactuator, such as might occur by relief of pressure in or application ofpressure to some other device served by the same hydraulic system, wouldcause a release of the lock. The springs 31 are strong enough to retainparts in locked position, under such circumstances, and untilapplication of full pressure to effect unlocking and movement of thepiston.

I claim as my invention:

1. In combination with a cylinder, a piston slidably fitted therein forreciprocation between two limit positions, and means to admit fluidunder pressure to and to discharge such fluid from the respective endsof the cylinder, to effect reciprocative movement of the piston byapplication of pressure forces to its respective faces, two lockingdevices, one adjacent each face of the piston, and each including alocking dog means guided in the piston for radially outward movementinto locking position and inward movement into retracted, unlockedposition, a toggle link rockably engaged by one end with the locking dogmeans, and a fulcrum member mounted in the piston and shiftable axiallyrelative to the piston, whereon the other end of the toggle link isfulcrumed, yieldable means reacting between the piston and the fulcrummember of each locking device, biasing the fulcrum member towards aposition wherein the toggle link is aligned with its dog means and thedog means is projected and retained in its projected position, the outertip of each dog means being beveled, and the cylinder wall beingcorrespondingly beveled in position to be engaged by the bevel of acorresponding dog means, when the piston reaches one limit position andthe dog means is projected, and to be retained in such locked positionso long as the projected dog means and the toggle link remain aligned,and a pressure-actuated member operatively connected to said fulcrummember, and located to be subject to and moved by a pressure forceacting upon a given face of the piston to move the piston towards theopposite limit position, thereby to move the fulcrum member in the axialsense to shift the toggle link from alignment with the dog means, and soto enable retraction of the dog means under the influence of the samepressure force tending to move the piston, acting through the dog meansbeveled tip.

2. The combination of claim 1, wherein the piston is recessed axially ateach pressure face to define a lock cylinder, and the fulcrum member isslidably fitted as a plunger into said lock cylinder, and exposed tomain cylinder pressure exteriorly of the lock cylinder, to constitutealso the pressure-actuated member, the interior of each lock cylinderbeing vented to the opposite face of the piston.

3. The combination of claim 1, wherein the dog means comprises acircular segmental ring, the piston being circumferentially grooved foraxial projection and retraction of said rings segments, the outercircumferential edge of the ring being beveled, and the cylinder wallbeing correspondingly circumferentially beveled for locking engagementwith the ring, when projected, and the dog means further including aplurality of expander elements distributed angularly about the pistonsaxis and guided in the piston for radially outward and inward movement,into and from alignment with corresponding toggle links, said expanderelements being operatively engaged with the rings segments to project orto enable retraction of the latter.

4. The combination of claim 3, wherein the adjoining ends of the ringsegments are oppositely beveled, and the expander elements arecomplementally double-beveled, to urge apart and outwardly the ringsegments upon radial outward movement of the expander elements.

5. In combination with a guide element and a cooperating element guidedtherein for reciprocative movement between two limit positions, theguide element having two surfaces, one at each limit position, each ofwhich is beveled with relation to the direction of reciprocation,

means to lock the two cooperating elements in each such limit position,comprising axially spaced locking dog means each carried and guided bythe guided element for movement transversely of the direction ofreciprocation between a projected locking position and a retractedunlocked position, each dog means having a beveled tip surfacecomplemental to the beveled surface at the corresponding end of theguide element, and being positioned for locking interengagement of thecorresponding beveled surfaces when parts are in the respective limitpositions, two toggle devices carried by the guided element andoperatively engaged each with its corresponding dog means to move thelatter into projected position as the toggle device rotates intoalignment with the direction of movement of its dog means, stop means toretain the toggle devices in such aligned position, means to rotate eachtoggle device, independently of the other, from such aligned position,and means operable simultaneously with application of such rotativeforce to a given toggle device, to apply a force to the guided elementin the sense tending, through the interengaged beveled surfaces, toeffect retraction of the projected dog means to its unlocked position,and consequent rotation of the toggle device from its aligned position,and finally to effect movement of the guided element towards theopposite limit position.

6. The combination of claim 5, wherein the guide element and the guidedelement constitute a pressure fluid actuator, and fluid pressure meansare arranged to apply force to the guided element and to the respectivetoggle means, to rotate that one into aligned position which will engageat the limit position towards which the guided element is caused toadvance by such application of force.

'7. In combination with a closed cylinder formed for admission ofpressure fluid to, and discharge of such fluid from, its two ends, andformed also with a circumferentially directed beveled groove adjacenteach end, a piston fitted within said cylinder for reciprocativemovement, said piston having two non-communicating axial bores openingto its respective faces, and a plurality of radial guide aperturesintersecting each bore near the exterior end thereof, and said pistonbeing also formed with two circumferential grooves, one adjacent eachend, into which its radial guide apertures open, a plunger fitted intoeach axial bore for axial sliding movement, to seal off a pres-. surechamber at the bottom of the respective bores, expander elementsreceived and radially slidable in the respective radial guide apertures,toggle links operatively inter-connecting each plunger and the expanderelements at the corresponding ends of the piston, each toggle link beingrotatively connected with each of its expander element and its plungerfor rotation into and from alignment with said expander element byreciprocation of the plunger in the axial direction, and a segmental,substantially circular locking ring, beveled complementally to thecylinders corresponding circumferential groove, received in each of thepistons circumferential grooves, for projection from the pistons grooveinto engagement with the cylinders groove, and for retraction within thepistons groove, the expander elements and the corresponding locking ringsegments being operatively interengaged for projection of the ring uponoutward movement of the expander elements as their toggle links comeinto alignment with the latter, and ports communicating between eachpressure chamber and the opposite face of the piston, for biasing of thetoggle links and their associated parts at one face of the pistontowards locked position during movement of the piston under theinfluence of fluid pressure applied to its other face, and for ventingeach pressure chamber behind its plunger, upon application of pressureto the opposite face of such plunger.

8. The combination of claim 7, wherein each expander element isdouble-beveled, and is located radially inwardly of the adjoining endsof two ring segments, such ring segment ends being beveledcomplementally to the bevels of the expander element, to constitute theoperative interengagement for projection of the ring.

9. The combination of claim 7, including compression springs reactingbetween the piston and each plunger, biasing each such plungeryieldingly in the sense to urge the toggle links and their associatedpart-s towards locked position.

10. 'In combination with a closed cylinder formed for admission ofpressure fluid to, and discharge of fluid from, its respective ends, andformed also with a beveled shoulder adjacent each end, a piston fittedwithin said cylinder for reciprocative movement under the influence offluid pressure applied to its respective faces, said piston having twonon-communicating axial bores opening to its respective faces, and aplurality of radial guide apertures intersecting each bore near theexterior end thereof, a plunger fitted into each axial bore for axialsliding movement relative to the piston, to seal off a pressure chamberat the interior end of the respective bores, projectible and retractablemeans at each end of the piston, including elements radially movable inthe guide apertures, to interengage with the cylinders beveled shoulderat the corresponding end, and complement-ally beveled toggle linksinterconnecting the plunger at each end and the corresponding radiallymovable elements, to urge the latter outwardly as such toggle links areurged toward alignment with the radially movable elements, and fluidports connecting each pressure chamber in the piston with the pistonsopposite face.

References Cited in the file of this patent UNITED STATES PATENTS1,842,776 "Bogslowsky Jan. 26, 1932

